With JavaScript and the V8 engine at the core, an event-driven architecture, and scalability out of the box, Node.js has quickly become the de facto standard for creating web applications and SaaS products. Node.js frameworks such as Express, Sails, and Socket.IO allow users to quickly bootstrap applications and focus only on the business logic.

Node.js owes much to JavaScript for its enormous popularity. JavaScript is a multiparadigm language that supports many different styles of programming, including functional programming, procedural programming, and object-oriented programming. It allows the developer to be flexible and take advantage of the various programming styles.

But JavaScript can be a double-edged sword. The multiparadigm nature of JavaScript means that nearly everything is mutable. Thus, you can’t brush aside the probability of object and scope mutation when writing Node.js code. Because JavaScript lacks tail call optimization (which allows recursive functions to reuse stack frames for recursive calls), it’s dangerous to use recursion for large iterations. In addition to pitfalls like these, Node.js is single threaded, so it’s imperative for developers to write asynchronous code.

JavaScript can be a boon if used with care—or a bane if you are reckless. Following structured rules, design patterns, key concepts, and basic rules of thumb will help you choose the optimal approach to a problem. Which key concepts should Node.js programmers understand? Below I’ll share the 10 JavaScript concepts that I believe are most essential to writing efficient and scalable Node.js code.